It's not over till it's over: a narrative review of Long COVID

Viral persistence following acute COVID infection is increasingly being reported by patients and gradually being recognized as a medical syndrome. Like much about COVID, this so-called Long COVID is perplexing. It is associated with numerous symptoms. foremost among them profound fatigue, and often occurs in a relapsing/remitting pattern. There is one "living" guideline for managing Long COVID and even terminology and definitions of the syndrome are in flux. Long COVID occurs inpatients who have recovered from the acute infection and this may be viral persistence, a form of autoimmunity, or the long-term results of organ damage sustained during the acute infection. Symptoms have been reported up to six months after acute infection with no clear association between the severity of the acute infection and the presence or absence of Long COVID. The symptoms of the acute illness do not necessarily align with the symptoms of Long COVID. Disruptions to the autonomic function in Long COVID are particularly puzzling, including orthostatic intolerance syndrome (which may not have occurred during the acute infection). Loss of the sense of smell and taste is one symptom that appears common in both acute and Long COVID; on the other hand, fever is more prevalent in acute than Long COVID. Research is urgently needed to better understand Long COVID, for example: what is the role of elevated biomarkers such as D-dimer and C-reactive protein in Long COVID? Is Long COVID one or more than one syndrome? How can patients with Long COVID be appropriately treated?